This invention relates to a process for producing fluosulfonic acid from hydrogen fluoride and sulfur trioxide.
British Pat. specification No. 496,658 discloses a process for manufacturing fluosulfonic acid comprising continuously passing SO.sub.3 and HF in equivalent quantities through a reaction tube. It is stated that the reactants may both be liquid or gaseous or one may be liquid and the other gaseous.
U.S. Pat. No. 2,430,963, issued to Stephenson et al. on Nov. 27, 1944, is directed to a process for making fluosulfonic acid by combining a substantially anhydrous liquid consisting of fluosulfonic acid and dissolved HF with a substantially anhydrous liquid mixture consisting of fluosulfonic acid and dissolved SO.sub.3. The liquor containing HF is made by feeding anhydrous HF gas into contact with fluosulfonic acid in any suitable gas-liquid contacting apparatus. The liquid mixture containing SO.sub.3 can be made by distilling commercial oleum in such a way as to form a substantially 100% SO.sub.3 gas and dissolving the SO.sub.3 in fluosulfonic acid.
In general, processes involving reaction of HF and SO.sub.3 gases require bulky gas handling and absorbing facilities. Removal of latent heats of gaseous reactants is also necessary. Moreover, since HF and SO.sub.3 are usually shipped in the liquid state, gas phase reactions require additional equipment and energy expenditure to convert the liquids to the gaseous state. Producing a fluosulfonic acid product which does not contain a significant excess of one of the reactants is difficult because of the substantial solubility of both HF and SO.sub.3 in fluosulfonic acid, fluctuation in the HF and SO.sub.3 content of commercial raw materials, and mchanical difficulties mechanical controlling the end point of the reaction. Moreover, the particular reactant in excess and the amount of it are often uncontrollable and result in a product of inconsistent composition. Hence, there is a continual need in the art for processes which allow the production of fluosulfonic acid of controllable purity.